A lock and keeper set is already disclosed in EP-B-0 963 498 by the applicant. The lock disclosed in this European patent is fixed by means of externally threaded bushings against a first side of a tubular upright of a hinged gate so that the latch and dead bolt extend through the upright. The externally threaded bushings are applied over the latch and the dead bolt and are screwed through the same holes in the tubular upright into the frame of the lock.
EP-A-1 367 198, also filed by the applicant, discloses a similar lock wherein the bushings for securing the lock to the tubular upright are however internally threaded. These bushings are also applied over the latch and the dead bolt but are screwed onto an externally threaded tubular part of the frame instead of in the frame. In still a further variant of the lock disclosed in the above-mentioned patents, the lock is fixed by separate screws applied through holes next to the latch and dead bolt through the tubular upright of the gate.
The above-described prior art locks are especially intended for being applied to gates in fences around gardens, swimming pools, etc. This means that the locks and/or the keeper devices are usually fixed to poles. A problem with such applications is that it is rather easy to force the lock open by inserting a crowbar or similar instrument between the gate and the fixed member to which the keeper device is secured. The fixed member and the gate can more particularly be forced apart quite easily until the bolt is withdrawn from the keeper. A solution which is applied in practice consists in applying a chain and a padlock around the fixed member and the gate. However, such an additional locking system is not aesthetic and is quite cumbersome to apply.
Locks with security means for preventing opening of a door by inserting a jimmy or similar instrument between the door and its jamb and springing the door and jamb apart until the latch bolt is withdrawn from its strike plate are already known in the early nineteen-hundreds. Reference can be made for example to U.S. Pat. No. 1,325,919, U.S. Pat. No. 1,359,347 and U.S. Pat. No. 1,462,828. The locks disclosed in those patents are however rim locks which are mounted against the front face of the door. In these locks, the bolt does not have to extend through an upright of the door. To provide the additional security, the housing of the lock is constructed to engage behind the keeper device when closing the door.
It would therefore be advantageous to provide a new lock and keeper set which makes it much more difficult to force the lock open.